1. Field of the Invention
The present invention relates to a single-wafer type thin-film deposition apparatus which deposits a thin film onto a substrate to be treated. The present invention particularly relates to a gas-feeding apparatus adapted to be installed in an thin-film deposition apparatus.
2. Description of the Related Art
As for a thin-film deposition apparatus used for atomic layer growth processing, material gases can be fed onto a substrate surface at a uniform gas concentration using a showerhead system. In contrast, in a laminar flow system, gas concentrations upstream and downstream of a gas controller tend to vary. To feed gases uniformly onto the substrate surface using a showerhead, material gases are fed from a distribution plate having relatively small conductance after the gases pool inside the showerhead. Consequently, after a first gas is fed, the first gas remaining is exhausted by feeding a second gas, and then a third gas is fed. When the third gas is fed, if the first gas still remains, solid matters are formed by a vapor-phase chemical reaction. For this reason, when the third gas is fed, it is required to exhaust all the remaining gas within the distribution apparatus thoroughly. Particularly, when a material gas with a low vapor pressure is used, an exhaust time required for exhausting the remaining gas increases.